Flask



FIG. 1 is a perspective view of a flask, showing my new design;

FIG. 2 is a side view thereof;

FIG. 3 is an opposite side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a top view thereof. 

CLAIM The ornamental design for a flask, as shown and described. 